The present invention relates generally to proportional fluid control valves, and most advantageously to four-way, proportional pressure control valves having self-regulating capabilities.
Various fluid control valves have been frequently provided in the prior art for controlling the operation of a fluid system, such as a fluid-powered cylinder or other fluid-powered device, in which a control fluid pilot operator system is used to effect operation of the control valve. Many of such fluid control valves have been proportionally controllable, but such control valves have not typically provided for accurate, self-regulating, proportional control such as that necessary for use in devices such as industrial robots, or other such devices, where close control and regulation is desired or necessary. Although proportionality is frequently achieved through the use of variable regulators, or the like, such devices are relatively expensive and thus limit the application of such valves, especially in pneumatic pilot operator systems where proportional control is desired or required. Furthermore, even where such proportionality has been achieved in less expensive ways, such valves or systems have typically not been self-regulating, at least without resort to expensive, complicated, or relatively imprecise associated systems or apparatuses.
Therefore, one of the principal objects of the present invention is to provide an improved, four-way, self-regulating control valve that is relatively simple and inexpensive, and that provides for more closely regulated proportional pressure control wherein relatively small spool or valve member movements result in relative pressure differences, thus providing for corrective spool or valve member movement to maintain desired output pressures. It should be noted that the principles of the invention are also applicable to other types of control valves, including but not limited to two-way and three-way valves. Another object of the present invention is to provide such a self-regulating control valve that is programmable and capable of variable load pressures, either prior to operation or during operation, and that requires substantially no pilot control flow or other signal input at its center-off, or neutral, condition.
It is also an object of at least some versions of the present invention to provide for infinite load pressure selectablility, or in other versions of the present invention, to provide for a pulse-width modulated input signal in order to cause pilot control pressures to vary differentially, with control flow outlet being proportional to the differential pilot signals.